I'm not trying to put you down, but seriously, take off the blinkers and look at the gun with fresh eyes. It's the easiest thing in the world to get a picture and cut out a gun, but the gun will always suck. Extruding polylines is only 1 technique, it allows you to make shapes quickly and easily, but you have to do more than that. I would suggest learning how to make cylinders, and how to take your extrusions to the next stage, adding details etc.
Most FPS games have the gun pointing forward, so always think about how the gun will look when in-game. It can help you decide where to spend detail - spend polygons on the areas that are shown the most. Don't waste polygons on the handle, use cylinders for barrels. One thing that is pretty vital, at least for a couple of models, is to have a model, airsoft, or even a toy gun - then replicate that as accurately as you can. Having a gun model to analyse makes all the difference. Really, you can't model a gun based on a side view, theres too much detail lost. With practice you'll get better, I think everyone starts out with cut-outs. Really though, it's a lot more fun to be a bit clinical with it, study the gun and work out it's moving parts, it's components, how are bullets ejected, etc.
I don't make weapon models very often, but when I do it's an airsoft and a micrometer and a good dose of determination. I use Rhino3D which is a great modelling package for making guns (NURBS, so perfect CSG, makes modelling so much easier and exact). I'm not sure how good Blender is for weapon modelling, I could never get into Blender. Maybe there's an alternative package that is more dynamic for this sort of modelling.
It takes time, but all good weapon models take time. A professional might only have to make 1 weapon per week, imagine spending 20-40 hours on a handgun model - that's the workload that is needed to get pro results. If you spent 2 hours making your gun, imagine spending 10 times as much time, adding 10 times as much detail and accuracy. You'd come out with a much better model of course, something that you'd post here and people would commend you on.
Health, Ammo, and bacon and eggs!
